1. Field of the Invention
The present invention relates to a novel process for the preparation of organic esters, and, more especially, relates to a process for the preparation of ethyl or isopropyl carboxylates by reacting a carboxylic acid with ethylene or propylene, respectively.
2. Description of the Prior Art
It has long been known that carboxylic acids react with and are esterified by olefins in the presence of acid catalysts. Although the advantages of this method for the synthesis of esters, compared to the conventional processes utilizing alcohols and inorganic acid catalysts in the liquid phase, were quickly recognized, such method has nevertheless remained a laboratory curiosity, notably in an ethyl carboxylate synthesis, because of certain difficulties encountered in the course of the reaction.
In fact, as has been earlier reported [Ind. & Eng. Chem., 1951, 43, pages 1596-1600 and J. Appl. Chem., 1963, pages 544-547], ethylene can only be esterified by a carboxylic acid, in the presence of an acid catalyst, under extremely severe conditions. These extremely harsh conditions, moreover, promote various secondary reactants, in particular polymerization reactions, which reactions compete with the esterification at the expense of the yield of the desired ester.